CAN THE RED RECTANGLE MOLECULAR-EMISSION BANDS BE ASSIGNED TO C-3

We review the current information on the unique group of visible emiss ion bands known as the Red Rectangle bands (RRBs). A laboratory spectr um exactly matching these bands is not yet available; however, there i s sufficient reason to hypothesize phosphorescence from C-3 as the sou rce. The points in favor of the C-3/RRB hypothesis can be summarized a s follows: (1) The RRBs are found in the spatial location where carbon aceous grains are being impinged upon by a bipolar outflow. (2) C-3 is known to accompany circumstellar carbon grains and may constitute a ' magic' fragment in the UV photofragmentation of C-n clusters. (3) Our recent observation of the spin-forbidden CO Cameron emission bands in this object suggests that charged particle impact excites triplet stat es. (4) The energy of the lowest triplet state of C-3 is known to be v ery close to that of the RRBs. (5) The RRBs display a vibrational spac ing that is quantitatively consistent with C-3, including a rare negat ive anharmonicity.